Interlock



Feb. 14, 1950 E. B. cAlN 2,497,487

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y :i 47 f7 f7@ j; v i 4/ l L l f3 f UL Y j; i* Uh wwf* im U if ha@ l. H; Il@ Eimer. Caz'zz Patented Feb. 14, 1950 UNITED STATES PATENT OFFICE INTERLOCK Delaware Application May 1, 1946, Serial No. 666,473

1 Claim.

This invention relates to safety systems and devices for electrical apparatus and has special reference to the provision of improvements in so-called interlocks for preventing access to the interior of a high voltage compartment so long as the power is on.

In the design of television receivers and other high voltage apparatus for use in the home the practice has been to duplicate the door-switch interlocks commonly employed in high powered commercial installations. Irrespective of the advantages claimed for such interlocks it may be said, generally, that they are more expensive than is desirable in low-cost radio and television receivers and, furthermore, are not always reliable since, through long non-use, the springs or other movable parts of the switch may stick and fail to operate.

Accordingly, the principal object of the present invention is to provide an interlock having no springs or other movingr parts and one characterized by its reliable performance and by its rugged yet simple and inexpensive construction.

Another and related object of the present invention is to provide a chassis incorporating an improved power cord interlock which dispenses with the necessity of the full cabinet back conventionally employed in television receiving sets and analogous high voltage installations, and one which shall nevertheless comply in all respects with the safety requirements dictated by the U. S. Board of Fire Underwriters.

Another and specific object of the present invention is to provide a combined strain-relief and interlock for a power cord.

The invention will be described in connection with the accompanying drawing, wherein: Fig. 1 is a side elevation, partly in section, of a television receiver chassis including a power cord interlock and incorporating the invention, and Fig. 2 is a front elevation of the power cord connector of Fig. 1.

In the embodiment of the invention which has been selected for purposes of illustration I designates one of the four side walls and 3 the top of a sheet metal chassis or compartment 5 which will be understood to house the wiring and miscellaneous parts of a television receiver or the like. Certain replaceable high voltage parts of the receiver, exemplied by a vacuum tube I and a transformer 9, are mounted on the top surface 3 of the chassis and are enclosed on all sides and at the top by a removable cover II which rests upon the outer top surface 3 of the chassis. A dependent extension IIa of one of the side walls of the cover II overlaps the side wall I of the lower compartment 5 and is preferably held in position thereagainst by two screws I3.

A power cord I5 for energizing the transformer 9, and hence the other parts of the set terminates in a moulded rubber or similar fixture I'I having a circumferential flange Ila which is permanently affixed to the dependent portion IIa of the cover II as by means of rivets I9. The rivets I9 and the screws I3 thus provide a strain-relief for the cord or cable I5. In the instant case the power cord fixture I'I comprises a socket portion I'Ib which extends through a pair of aligned apertures IIb and Ib in the overlapping sides IIa and I. The socket IIb is provided with a pair of metal jacks I'Ic for receiving the complementary prongs 2Ic of a plug-type connector 2I which is permanently affixed, as by rivets 23, to the side wall I of the lower compartment 5 and spans the aperture Ib therein. Two wires 25 which may be soldered to the inner terminals of the prongs 2Ic conduct the power from the cord I5 to the transformer 9 when the cover I I is on its base 3 and the separable parts of the socket type connector I'I, 2I are connected. With the said parts thus arranged it is impossible to remove the cover I I from its anchorage I3 at the side of the chassis I without breaking the electrical connection between the terminals I'Ic and 2 Ic.

When it is desired to remove the cover II for the purpose of inspecting the high voltage units which are mounted therebeneath it is merely necessary to remove the screws I3 and to pull the terminal Il of the cord I5 away from the chassis a distance suicient to disengage the jacks IIc from the prongs 2Ic. Since the terminal Il is secured (by the rivets I9) to the dependent portion IIa of the cover II the above described movement causes the cover to slide a similar short distance on its base 3, whereupon the cover may be raised and removed to exposegthe deenergized high voltage apparatus I an What is claimed is:

In apparatus of the character described, a chassis defining a walled enclosure, high voltage apparatus mounted on the exterior surface of one wall of said enclosure, electrical connections for said high voltage apparatus extending through said wall and terminating in contacts adjacent to the exterior surface of an adjacent wall of said enclosure, a cover defining a compartment for said high voltage apparatus removably mounted on the exterior surface of said rst mentioned wall and overlapping said ad- ELMER B. C'A'I.

4 REFERENCES CITED The following references are of record in the le of this patent:

5 UNITED STATES PATENTS Number Name Date 2,175,025 Hooven Oct.. 3, 1939 2,209,213 Vernon July 23, 1940 2,232,746 Van Emden Feb. 25, 1941 

